1. Field of the Invention
The present invention is concerned with a communication system using mobile IP and pertains in particular to a mapping method for home addresses and care-of addresses in the Home Agent.
2. Description of the Related Art
In the document “IP Mobility Support in IPv6” (David B. Johnson, draft-ietf-mobileip-ipv6-24.txt, December 2003) under examination in the Internet Engineering Task Force (IETF), hereinafter called “Mobile IP”, a terminal communicating with a Mobile Node sends an IP (Internet Protocol) packet with the destination IP address set to the home address of the Mobile Node. The IP packet routed to the home network of the Mobile Node is captured by the Home Agent of the Mobile Node, encapsulated, and forwarded to the movement destination foreign network. In order to encapsulate the packet and forward it to the Mobile Node, the Home Agent receives in advance a binding update from the Mobile Node and manages the correspondence relationship between the home address of the Mobile Node and its IP address acquired in the foreign network (below called the “care-of address”). In this way, it becomes possible for the Mobile Node to receive, in the foreign network, the IP packet having as its destination the home address.
In addition, regarding packet filtering, product development of gateway devices performing packet filtering by explicitly setting the IP address and port number and protocol is underway.